Alternator - 45amp or 80amp?

[RichardS]

Luke motorsport have some good looking alternators - I want to replace the original dynamo on my 1973 Sprint. http://lukemotorsport.co.uk/lukemotorsportua.html

They seem very reasonably priced - ?28 for the 45amp and ?36 for the 80amp [they also do a gear reduction starter for ?105 which is a lot cheaper than some of the suppliers].

My question is 45amp or 80amp? Is it the more ampage the better or will my wiring melt!!

Richard

[gordonlund]

Richard,

45 amp is plenty. The original Lucas AC17 alternator gave 36 amps against the Lucas C40 dynamo of 22 Amps.

An 80 amp alternator may have problems in fitting too close to the exhaust manifolds. It should not cause any electrical problems assuming your wiring is sound. Any faults in the wiring could be made worse by passing 80 amps through wiring only sized for 36.

Gordon

[GrUmPyBoDgEr]

As Gordon mentioned, make sure that all of your wiring is up to the job first.
The Lucas units tend to be a bit bulky & finding space for the 80A unit will probably be difficult.
Check out other suppliers who's units are based on the Nippon Denso alternators. These take up a lot less room.
I have an 80A unit out of a Toyota fitted to my Zetec in an Elan & have had no problems except for the charging light function which refused to go out, so I pulled the plug
The conversion that I did included a modern wiring harness, so no problems.
You wil have to sort out the necessary mounting bracket & fan belt tensioner to suit the chosen alternator.
Poly-V pulleys can usually be replaced with single V pulleys from the original supplier.
John

[GrUmPyBoDgEr]

Deleted. Entered2 x

[RichardS]

Thanks John and Gordon

I will go for the 45amp. The Luke motorsport one is brand new and a direct replacement for the Lucas one and costs less than a refurbished Lucas LR100A!

Richard

PS any ideas on suppliers of the mounting brackets? I see TT does one for ?30 ie more than the cost of the alternator!!

[GrUmPyBoDgEr]

Sorry I can't help regarding sourcing bracketry.
I made my own customised bits.
John

[RichardS]

Unfortunately my metal fabricating skills are almost non existent!

Richard

[Barney]

I saw a solution to this on one of the Lotus websites - possibly the golden gate club.
The original bracket was retained on the engine with a length of suitable stud bar running the length. The deal is to use Nylock Nuts & washers on the stud bar to position the alternator (normally with a narrower spacing between brackets) in between, or inside, the existing long dynamo bracket ends.
You are aiming to align the pulleys, any misalignment will give excessive wear of belt & who knows what else!
This may be a bit fiddly --- but Hey! if it works . . .

Cheers
Barney

[freddy22112211]

An 80A alternator will of course need nearly twice the power to drive it as a 45A one (when supplying 80amps).
Gordon

[bcmc33]

I can't imagine what would be needed to for an 80amp demand.

If anyone has any ideas - please advise.

[fatboyoz]

[PS any ideas on suppliers of the mounting brackets? I see TT does one for ?30 ie more than the cost of the alternator!![/quote]

Paul Matty also, but similar price to TTR.
Colin.

[Barney]

I can't imagine what would be needed to for an 80amp demand.

If anyone has any ideas - please advise.

Open top, showery weather, electric heated passenger seat modification, maybe a little salt, perhaps the heated bikers underwear previously suggested . . .

"Do you want to come for a quick burn up dear?"

Marriage counseling at its best

[GrUmPyBoDgEr]

80 A is a lot of juice considering the limited requirements of our lovely little ol' cars.
My choice for an alternator of that rating was quite simple.
That size is very common in modern cars. It also cost me nothing
My Nippon Denso alternator is nice & small making the instalation easy.(The Zetec has Poly-V pulleys).
Also to use a commonly mentoned quote "it adds lightness.
Nippon Denso also make lovely little(much lighter) lower amperage Alternators which may also be of interest to you guys, that's if originality is not high up on the ladder.

The marraige counseling may have been of some use to me a few years ago.
My biggest worry these days is getting an MOT for my baby
John

[denicholls2]

While it's true that if your wiring is standard and up to snuff, adding a larger alternator may not be problematic, things change in a hurry if you rearrange other parts of the electrical system, for example to turn on both beams simultaneously.

Whereas you may have been battery-limited in the impact of this prior to adding a better alternator, you're now capable of supplying 35 more amps to any undersized wiring -- with the result that you may fry it where you couldn't before.

Until you check the wire size on involved segments in the system to confirm I'm overcautious, you must assume that wiring (to the ammeter, for example) may not have been designed to carry more than 45 amps. Your ammeter may not be so designed, either.

I could be overcautious here, but the consequences are expensive. And the temperature of many wires in my Europa circuits suggests I'm not overcautious.

[ncm]

Hi Richard, the easiest way to mount an ACR alternator is to source the bracket that Ford used for the Escorts etc. It may not be as robust as the Lotus item but I have used them for many years without any problems.You may find that the dynamo adjusting strap is also re-useable.


Cheers, Brian.